US4030903A - Exuded transition metal films on glass-ceramic articles - Google Patents
Exuded transition metal films on glass-ceramic articles Download PDFInfo
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- US4030903A US4030903A US05/644,130 US64413075A US4030903A US 4030903 A US4030903 A US 4030903A US 64413075 A US64413075 A US 64413075A US 4030903 A US4030903 A US 4030903A
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- glass
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- transition metal
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- 239000002241 glass-ceramic Substances 0.000 title claims abstract description 25
- 229910052723 transition metal Inorganic materials 0.000 title claims description 23
- 150000003624 transition metals Chemical class 0.000 title claims description 23
- 239000000203 mixture Substances 0.000 claims abstract description 55
- 239000011521 glass Substances 0.000 claims abstract description 36
- 229910000314 transition metal oxide Inorganic materials 0.000 claims abstract description 28
- 238000002425 crystallisation Methods 0.000 claims abstract description 21
- 230000008025 crystallization Effects 0.000 claims abstract description 20
- 230000005291 magnetic effect Effects 0.000 claims abstract description 15
- 230000008018 melting Effects 0.000 claims abstract description 11
- 238000002844 melting Methods 0.000 claims abstract description 11
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 8
- 230000003197 catalytic effect Effects 0.000 claims abstract description 8
- 150000003623 transition metal compounds Chemical class 0.000 claims abstract 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 44
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 36
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 36
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims description 28
- 150000001875 compounds Chemical class 0.000 claims description 23
- 229910018404 Al2 O3 Inorganic materials 0.000 claims description 21
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 20
- 239000007789 gas Substances 0.000 claims description 20
- 239000011572 manganese Substances 0.000 claims description 19
- 229910052681 coesite Inorganic materials 0.000 claims description 18
- 229910052906 cristobalite Inorganic materials 0.000 claims description 18
- 239000000377 silicon dioxide Substances 0.000 claims description 18
- 229910052682 stishovite Inorganic materials 0.000 claims description 18
- 229910052905 tridymite Inorganic materials 0.000 claims description 18
- 229910015133 B2 O3 Inorganic materials 0.000 claims description 16
- 229910016764 Mn3 O4 Inorganic materials 0.000 claims description 16
- -1 NiAl2 O4 Inorganic materials 0.000 claims description 15
- 229910052644 β-spodumene Inorganic materials 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 14
- 239000013078 crystal Substances 0.000 claims description 13
- 239000000654 additive Substances 0.000 claims description 12
- CNLWCVNCHLKFHK-UHFFFAOYSA-N aluminum;lithium;dioxido(oxo)silane Chemical compound [Li+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O CNLWCVNCHLKFHK-UHFFFAOYSA-N 0.000 claims description 12
- 229910017368 Fe3 O4 Inorganic materials 0.000 claims description 11
- 229910017344 Fe2 O3 Inorganic materials 0.000 claims description 10
- 229910021305 CoAl2 Inorganic materials 0.000 claims description 9
- 239000012298 atmosphere Substances 0.000 claims description 9
- 230000005294 ferromagnetic effect Effects 0.000 claims description 9
- 229910021274 Co3 O4 Inorganic materials 0.000 claims description 8
- 229910011763 Li2 O Inorganic materials 0.000 claims description 8
- 238000010899 nucleation Methods 0.000 claims description 8
- 230000006911 nucleation Effects 0.000 claims description 8
- 230000003647 oxidation Effects 0.000 claims description 8
- 238000007254 oxidation reaction Methods 0.000 claims description 8
- 239000006104 solid solution Substances 0.000 claims description 8
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 8
- 229910000500 β-quartz Inorganic materials 0.000 claims description 8
- 229910019096 CoTiO3 Inorganic materials 0.000 claims description 7
- 229910005451 FeTiO3 Inorganic materials 0.000 claims description 7
- 229910052731 fluorine Inorganic materials 0.000 claims description 7
- 229910019830 Cr2 O3 Inorganic materials 0.000 claims description 6
- 229910015370 FeAl2 Inorganic materials 0.000 claims description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- 229910003080 TiO4 Inorganic materials 0.000 claims description 6
- 239000000470 constituent Substances 0.000 claims description 6
- 229910052739 hydrogen Inorganic materials 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 6
- 229910052909 inorganic silicate Inorganic materials 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 5
- 229910019639 Nb2 O5 Inorganic materials 0.000 claims description 5
- 238000013329 compounding Methods 0.000 claims description 4
- 239000006060 molten glass Substances 0.000 claims description 4
- 229910004446 Ta2 O5 Inorganic materials 0.000 claims description 3
- 239000011651 chromium Substances 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 abstract description 12
- 229910000323 aluminium silicate Inorganic materials 0.000 abstract description 7
- 229910052596 spinel Inorganic materials 0.000 abstract description 6
- 239000011029 spinel Substances 0.000 abstract description 6
- 229910000502 Li-aluminosilicate Inorganic materials 0.000 abstract description 4
- 150000004760 silicates Chemical class 0.000 abstract description 2
- 238000011282 treatment Methods 0.000 description 31
- 239000006112 glass ceramic composition Substances 0.000 description 10
- 238000000576 coating method Methods 0.000 description 9
- 229910016583 MnAl Inorganic materials 0.000 description 8
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 6
- 238000011065 in-situ storage Methods 0.000 description 6
- 241000627951 Osteobrama cotio Species 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 5
- 239000011230 binding agent Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 229910002515 CoAl Inorganic materials 0.000 description 3
- 229910018563 CuAl2 Inorganic materials 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- 239000003245 coal Substances 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 229910016997 As2 O3 Inorganic materials 0.000 description 2
- 229910015372 FeAl Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 229910020068 MgAl Inorganic materials 0.000 description 2
- 229910004742 Na2 O Inorganic materials 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 2
- 229910004554 P2 O5 Inorganic materials 0.000 description 2
- 229910017895 Sb2 O3 Inorganic materials 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 239000006121 base glass Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000007767 bonding agent Substances 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000003279 ceramming Methods 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 239000006092 crystalline glass-ceramic Substances 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 239000006025 fining agent Substances 0.000 description 2
- 210000004185 liver Anatomy 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000015654 memory Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 229910052883 rhodonite Inorganic materials 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 241000894007 species Species 0.000 description 2
- 229910052566 spinel group Inorganic materials 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000000153 supplemental effect Effects 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 229910003321 CoFe Inorganic materials 0.000 description 1
- 229910002521 CoMn Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910018274 Cu2 O Inorganic materials 0.000 description 1
- PMVSDNDAUGGCCE-TYYBGVCCSA-L Ferrous fumarate Chemical compound [Fe+2].[O-]C(=O)\C=C\C([O-])=O PMVSDNDAUGGCCE-TYYBGVCCSA-L 0.000 description 1
- 241000264877 Hippospongia communis Species 0.000 description 1
- 229910000943 NiAl Inorganic materials 0.000 description 1
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 229910010340 TiFe Inorganic materials 0.000 description 1
- 229910007880 ZrAl Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 150000004645 aluminates Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000005816 glass manufacturing process Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 1
- YDZQQRWRVYGNER-UHFFFAOYSA-N iron;titanium;trihydrate Chemical group O.O.O.[Ti].[Fe] YDZQQRWRVYGNER-UHFFFAOYSA-N 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 239000005398 lithium aluminium silicate glass-ceramic Substances 0.000 description 1
- 229910000473 manganese(VI) oxide Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 239000002667 nucleating agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000006132 parent glass Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- ZNOKGRXACCSDPY-UHFFFAOYSA-N tungsten(VI) oxide Inorganic materials O=[W](=O)=O ZNOKGRXACCSDPY-UHFFFAOYSA-N 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
- C03C10/0018—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents
- C03C10/0027—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents containing SiO2, Al2O3, Li2O as main constituents
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
- C03C17/22—Surface treatment of glass, not in the form of fibres or filaments, by coating with other inorganic material
- C03C17/23—Oxides
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C2217/00—Coatings on glass
- C03C2217/20—Materials for coating a single layer on glass
- C03C2217/21—Oxides
- C03C2217/229—Non-specific enumeration
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C2217/00—Coatings on glass
- C03C2217/20—Materials for coating a single layer on glass
- C03C2217/21—Oxides
- C03C2217/23—Mixtures
Definitions
- Transition-metal-containing crystalline compounds of spinel structure are important constituents of inorganic coatings employed for an extremely wide variety of applications.
- iron-containing spinels such as magnetite (Fe 3 0 4 ), and also other ferrites such as manganese, cobalt and nickel ferrites, have been applied to a variety of organic and inorganic substrates in order to impart desirable electromagnetic properties thereto.
- Processes for applying such coatings and controlling the properties thereof in the course of deposition comprise a large body of technology and include vapor deposition, precipitation, evaporation and thermal decomposition techniques.
- transition metal oxides of spinel or ilmenite structure are included within the classes of catalytically-active compounds, and have been applied in the form of coatings to a variety of metal, glass and ceramic supports for use in catalytic processes.
- transition metal oxides useful in catalysis are Mn 3 O 4 , MnAl 2 O 4 , MnCr 2 O 4 , FeAl 2 O 4 , CoAl 2 O 4 , NiAl 2 O 4 , CoTiO 3 , MnTiO 3 , FeTiO 3 , CeTiO 4 , CuAl 2 O 4 and CuCr 2 O 4 .
- transition metal oxide coatings are employed in combination with inorganic substrates, coating adherence and durability are extremely important properties.
- binders are required to enable these coatings to demonstrate the toughness needed to withstand the shocks and abrasion of use.
- bonding agents or high sintering temperatures are required to obtain coatings demonstrating a useful degree of adherence to the support.
- magnetic recording media such as magnetic memory discs, extreme surface flatness is required, compounding the difficulty of providing a durable, adherent coating.
- the manufacture of glass-ceramics conventionally involves first compounding and melting a batch for a glass to which an amount of a crystallization-promoting or nucleating agent has been added, thereafter forming a glass article from the melt and cooling the article at least below the transformation range of the glass, and finally reheating the glass article according to a defined time-temperature schedule to produce internal nucleation and crystallization in situ thereof.
- the resulting article is uniformly crystallized, non-porous, free of voids, and retains the shape of the parent glass article.
- the present invention is based on the discovery that certain base glass-ceramic compositions, when modified by the addition of specified quantities of transition metal oxide modifiers, can be crystallized and thereafter heat-treated in a manner which will promote the formation and growth of transition metal oxide surface films thereon.
- glass-ceramic articles having integral surface films demonstrating desirable electrical, magnetic, light-absorptive and/or catalytic properties may be produced.
- the integral nature of these so-called exuded transition metal oxide films inherently provides the desired properties of adherence, durability and substrate compatibility.
- Transition metals suitable for inclusion in glass-ceramic base compositions according to the invention include manganese, iron, cobalt, copper, chromium, nickel and vanadium.
- useful crystalline phases which may be present in exuded transition metal oxide films produced according to the invention are Mn 3 O 4 , Co 3 O 4 , NiFe 2 O 4 , MnFe 2 0 4 , CoFe 2 O 4 , CuCr 2 O 4 , FeCr 2 O 4 , MnCr 2 0 4 , CoMn 2 0 4 , CoTiO 3 , Co 2 TiO 4 , MnTiO 3 , FeTiO 3 , VAlO 4 , CuAl 2 O 4 , CrAl 2 0 4 , NiAl 2 0 4 , FeAl 2 0 4 , CoAl 2 0 4 , MnAl 2 O 4 , Mn 2 Al 2 (SiO 4 ) 2 , MnNb 2 0 6
- exuded transition-metal-containing films produced according to the invention also demonstrate useful light reflecting and transmitting properties.
- Decorative films over a wide range of colors may be produced, or transparent or translucent bodies exhibiting sharp electromagnetic cutoff values may result.
- the end properties of the particular film produced depends on the composition of the base glass-ceramic composition selected as a support and upon the transition metal oxide additives selected for incorporation into the base composition.
- the capability of producing useful exuded transition-metal-containing films on glass-ceramics had been found to depend not only upon the composition of the glass-ceramic material selected as a base but also upon the nature of the subsequent treatment of the material to cause the formation and growth of useful exuded oxide films thereon.
- the formation and growth of transition-metal-containing oxide films is promoted by heat-treating transition metal-doped glass-ceramic articles under reducing conditions at elevated temperatures for a period of time sufficient to attain the desired degree of film growth.
- exuded transition-metal-containing films include not only films composed essentially entirely of transition metal oxide compounds such as MnAl 2 O 4 , Fe 3 O 4 , and the like, but also films wherein such compounds are in solid solution or combination with other crystalline species such as transition-metal-free aluminates, silicates, titanates, or similar compounds. Glassy matrix phases commonly found in semi-crystalline glass-ceramic materials produced from the crystallization in situ of glasses may also be present in these exuded films. In the preferred embodiments, however, crystalline transition metal oxide compounds normally comprise a predominate proportion (at least about 50% by volume) of the exuded film.
- a particularly useful class of base glass-ceramic compositions suitable for treatment according to the invention are the aluminosilicate and lithium aluminosilicate compositions characterized by the presence of beta-spodumene and/or beta quartz solid solutions as principal crystal phases.
- This base glass composition area includes compositions consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 55-80% SiO 2 , 14-35% Al 2 O 3 , 0-5% Li 2 O, 0-7% TiO 2 , 0-10% ZrO 2 , 3-13% total of TiO 2 + ZrO 2 , and 0-3% F, to which may be added a total of 0.1-10% of transition metal oxide additives.
- Suitable transition metal oxide additives include one or more oxides selected in the indicated proportions from the group consisting of 0-5% MnO 2 , 0-5% Fe 2 O 3 , 0-3% CoO, 0-2% CuO, 0-2% Cr 2 O 3 , 0-3% V 2 O 5 , and 0-10% NiO. Minor amounts of other compounds may, of course, be included within these compositions as aids in melting, to modify properties, or for other known purposes.
- additives which have been employed are La 2 O 3 , Nb 2 O 5 , BaO, B 2 O 3 , P 2 O 5 , MgO, CaO, ZnO, Na 2 O, K 2 O, Ta 2 O 5 , Cl, Br, As 2 O 3 , and Sb 2 O 3 .
- the total amount of these additives is generally held to not more than about 10% by weight, so that the basic constituents SiO 2 , Al 2 O 3 , Li 2 O, TiO 2 , ZrO 2 , F, and transition metal oxides will comprise at least about 90% by weight of the glass-ceramic composition.
- Glass-ceramic compositions within the above described composition range may be compounded and melted in accordance with conventional glass-making practice, and thereafter formed into glass articles by conventional means such as pressing, rolling, casting, spinning or the like.
- the batch materials may consist of oxides or may comprise any other compounds which will decompose at melting temperatures to yield molten batches having calculated oxide compositions within the aforementioned range.
- melting typically requires temperatures in the range of about 1600°-1650° C. for times in the range of about 6-16 hours.
- Glass articles formed from the above compositions may be converted by crystallization in situ into semi-crystalline glass-ceramic articles according to processes conventional for beta-spodumene and beta-quartz-containing glass-ceramics. Such processes comprise exposure of the articles to temperatures in the range of about 700°-800° C. for times in the range of about 1-4hours to obtain nucleation of the glass, followed by exposure to temperatures in the range of about 800°-1200° C. for times in the range of about 1-8 hours to obtain crystallization of the glass.
- Exuded films formed in the described composition system include one or more crystalline compounds selected from the group consisting of Co 3 O 4 ,Mn 3 O 4 , Fe 3 O 4 , NiAl 2 O 4 , CoAl 2 O 4 , MnAl 2 O 4 , FeAl 2 O 4 , VAl 2 O 4 , CuCr 2 O 4 , NiFe 2 O 4 , CoFe 2 O 4 , MnFe 2 O 4 , CoTiO 3 , MnTiO 3 , FeTiO 3 , Co 2 TiO 4 and CoMn 2 O 4 .
- the film-producing heat treatments suitably comprise heating at temperatures in the range of about 500°-1000° C. in a reducing atmosphere.
- Preferred atmospheres include hydrogen and hydrogen-containing atmospheres such as forming gas (H 2 , N 2 ). These atmospheres may contain additional constituents such as water vapor, CO, CO 2 , Cl 2 or sulfur. Of course, other conventional reducing atmospheres such as hexane, methane, ammonia or the like may also be employed if desired.
- Typical treatment times range from at least about 1/2 hour up to about 10 hours or more. Longer treatment times may be employed, if desired, but long treatments are of no practical benefit and are commercially undesirable.
- the transition metal oxide film After sufficient growth of the transition metal oxide film has been attained in accordance with the above-described treatment, it may be desirable to further treat the article to modify the properties of the surface film for certain applications. Leaching is sometimes useful to remove residual glassy phases and/or to modify the porosity of the film. Supplemental oxidizing and/or reducing treatments may also be employed to modify the oxidation states of certain of the film constituents. The precise nature of the supplemental treatment employed, if any, will depend on the properties desired in the film and the nature of the use for which the article is intended.
- thermally-crystallizable glass compositions suitable for forming beta-spodumene and beta-quartz glass-ceramics having exuded surface films containing transition metal oxide compounds according to the invention are set forth in Table I below.
- Compositions are given in parts by weight on the oxide basis as calculated from the batch. These compositions were batch melted in platinum crucibles at 1625° C. for 16 hours, and then poured into steel molds to form 4 inches ⁇ 4 inches ⁇ 1/2inches slabs and annealed at 650° C. Most of the compositions shown also include minor amounts of As 2 O 5 as a fining agent; however, the amount remaining in the glass after melting is negligible and is therefore not reported.
- the thermally-crystallizable glass articles in Table I, produced as above described, are thereafter treated as set forth below in Table II in order to produce glass-ceramic articles having beta-spodumene and/or beta-quartz solid solutions as principal crystalline phases and exuded surface films containing transition metal oxide compounds.
- Table II reports the crystallizing heat treatments employed to convert each thermally-crystallizable glass article to the semi-crystalline state, the principal crystal phase present in the articles after ceramming, the reducing heat treatments employed to promote the growth of transition metal oxide compounds present in the exuded surface films, the appearance of the articles after the growth treatments, and the dominant properties of the exuded films.
- the principal crystalline phases listed are generally solid solutions rather than specific compounds. In instances where forming gas is used as the reducing atmosphere, a gas consisting of 8% H 2 and 92% N 2 by volume was employed. Typical film thicknesses over the range of growth treatments employed range about 0.1-2 microns.
- compositions which are utilized for producing transition metal films having desirable magnetic and electrical properties are titania-nucleated lithium aluminosilicate compositions consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 58-64% SiO 2 , 19-21% Al 2 O 3 , 2-5% Li 2 O, 2-7% TiO 2 , 0-1% ZrO 2 , 3-7% total of TiO 2 + ZrO 2 , 0-1% F, and 1-6% total of transition metal additives, essentially including iron, selected in the indicated proportion from the group consisting of 1-5% Fe 2 O 3 , 0-5% MnO 2 , 0-5% CoO and 0-3% NiO.
- Exuded transition metal films produced from articles of these compositions typically include one or more compounds of spinel structure selected from the group consisting of Co 3 O 4 , Fe 3 O 4 , Mn 3 O 4 , MnAl 2 O 4 , FeAl 2 O 4 , CoAl 2 O 4 , MnFe 2 O 4 , NiFe 2 O 4 , and CoFe 2 O 4 , essentially including at least one iron compound.
- Example I of Table I represents the presently preferred composition for producing a film having particularly desirable magnetic properties according to the invention.
- compositions which are utilized for producing glass-ceramic articles having exuded transition metal oxide films demonstrating useful catalytic activity consist essentially, in weight percent on the oxide basis as calculated from the batch of about 68-74% SiO 2 , 14-19% Al 2 O 3 , 0-5% Li 2 O, 0-6% TiO 2 , 0-3% ZrO 2 , 5-9% total TiO 2 + ZrO 2 , 0-5% B 2 O 3 , 0-3% F, and 1-10% total of transition metal additives selected in the indicated proportion from the group consisting of 0-5% Fe 2 O 3 , 0-5% CoO, 0-5% MnO 2 , 0-2% CuO, 0-2% Cr 2 O 3 , and 0-3% NiO.
- Exuded transition metal films produced on articles of these compositions typically contain one or more compounds selected from the group consisting of CoTiO 3 , Co 2 TiO 4 CoMn 2 O 4 , Co 3 O 4 , Mn 3 O 4 , CoFe 2 O 4 , CoAl 2 O 4 , MnTiO 3 , and FeTiO 3 .
- Example 8 of Table I represents the presently preferred composition for producing a catalytically-active oxide film in this system.
- Types of glass-ceramic articles other than alumino-silicate and lithium aluminosilicate beta-quartz and beta-spodumene articles are also useful in providing exuded transition-metal-containing films according to the invention.
- Another useful composition area is found to include somewhat diverse silicate, aluminosilicate, and boroaluminate base compositions wherein manganese is a major constituent, comprising at least about 10% by weight of the compositions.
- the operative composition area includes compositions consisting essentially, in weight percent on the oxide basis, as calculated from the batch, of about 10-60% MnO 2 , at least one oxide selected in the indicated proportion from the group consisting of 10-70% SiO 2 , 13-43% Al 2 O 3 ,and 0-35% B 2 O 3 , essentially including at least about 5% B 2 O 3 and 20% Al 2 O 3 , when SiO 2 is absent, not exceeding about 5% B 2 O 3 when Al 2 O 3 is absent, and not exeeding about 10% B 2 O 3 when both SiO 2 and Al 2 O 3 are present, the sum total of MnO 2 + SiO 2 + Al 2 O 3 + B 2 O 3 comprising at least about 60% by weight of the composition, 0-30% Nb 2 O 5 , 0-20% TiO 2 , 0-5% Fe 2 O 3 , 0-10% NiO, 0--3% Cr 2 O 3 , 0-10% ZrO 2 , 0-35% La 2 O 3 , 0-10% Ta
- MInor amounts of other compounds may, of course, be included within these compositions as aids in melting, to modify properties and so forth, including, for example, Li 2 O, Na 2 O, WO 3 , P 2 O 5 , MgO, Cl, F, MnO 3 , Cu 2 O, V 2 O 5 , As 2 O 3 , and Sb 2 O 3 .
- Glass-ceramic compositions within the aforementioned composition range may be melted according to conventional practice, typically at temperatures in the range of about 1500-1600° C. for times on the order of about 6-16 hours.
- the molten glasses may be formed into glass articles by conventional means such as pressing, rolling, casting, drawing or the like. Batch materials for these glasses may comprise oxides or other compounds which will decompose at melting temperatures to yield molten batches having oxide compositions within the aforementioned range.
- Glass articles formed from the above compositions may be converted by crystallization in situ into glass-ceramic articles by heat treatment at temperatures in the range of about 600°-1200° C. for times in the range of about 4-24 hours.
- Useful crystallization treatments comprise a nucleation step wherein the article is heated at temperatures in the range of about 600°-800° C. for times on the order of 1-4 hours.
- Principal crystal phases in these composition systems include MnAl 2 O 4 , Mn 3 O 4 , Mn 2 Al 2 (SiO 4 ) 2 and MnSiO 3 depending somewhat on the composition of the MnO 2 -(B 2 O 3 , Al 2 O 3 , SiO 2 ) base glass.
- transition-metal-containing oxide films on the surface of these glass-ceramic articles is promoted using reducion heat treatments substantially the same as those above described for beta-spodumene and beta-quartz-containing articles.
- Such treatments typically comprise heating to temperatures in the range of about 500°-1000° C. in a reducing atmosphere, preferably an atmosphere comprising hydrogen or nitrogen-hydrogen forming gas, for treatment times in the range from about 1/2 hour up to about 10 hours, or more. Again, longer treatments may be employed if desired, but these are not deemed of practical benefit.
- Transition-metal-containing exuded films which may form in this composition system include Mn 3 O 4 , Fe 3 O 4 , MnAl 2 O 4 , NiAl 2 O 4 , NiFe 2 O 4 , MnFe 2 O 4 , MnCr 2 O 4 ,MnNb 2 O 6 NiNb 2 O 6 , Mn 2 Al 2 (SiO 4 ) 2 , and Ti 2 Nb 10 O 29 .
- the compounds in this system may be found either alone or in solid solution or combination with other crystalline species such as MnSiO 3 and ZrO 2 . Residual glassy phases may also be present.
- transition metal oxide films produced in these systems typically differ in composition from the interior of the article, it is possible that in certain cases the predominant surface compound is also one which predominates in the article as a whole. Nevertheless treatment according to the invention is effective to increase crystal formation in the surface layers of the article such that improved surface properties are obtained.
- thermally-crystallizable glass compositions suitable for forming silicate, aluminosilicate, and boroaluminate glass-ceramics having exuded surface films containing transition metal oxide compounds according to the invention are set forth in Table III below.
- Compositions are given in parts by weight on the oxide basis as calculated from the batch. The compositions were batch melted in platinum crucibles at 1600° C. for about 6 hours, and then poured into steel molds to form 3/8 ⁇ 5 ⁇ 5 inch slabs and annealed at about 600° C. A few of the compositions additionally contained minor amounts of As 2 O 5 as a fining agent, but the amount remaining in the glass after melting is small and is therefore not reported.
- the thermally-crystallizable glass articles of Table III, produced as above described, are thereafter treated as set forth below in Table IV in order to produce glass-ceramic articles having exuded surface films containing transition metal oxide compounds.
- Table IV reports the crystallization heat treatments employed to obtain bulk crystallization in situ of the articles, the principal crystalline phases present in the articles after ceramming, the reducing heat treatments employed to promote the growth of transition metal spinel films on the articles, the transition metal spinels present in the exuded surface films, the appearance of the articles after growth treatment, and the dominant properties of the exuded films.
- Film dielectric constant (K') and loss tangent (tan ⁇ ) are reported where determined on individual samples.
- aluminosilicate glass-ceramic compositions amenable to treatment according to the invention those consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 19-40% SiO 2 , 13-43% Al 2 O 3 , and 15-50% MnO 2 , optionally including 0-4% ZnO, 0-10% TiO 2 , 0-10% ZrO 2 , 0-10% SnO 2 , 0-10% NiO, 0-5% Fe 2 O 3 , and 0-30% Nb 2 O 5 , are preferred.
- compositions may provide exuded films containing at least one of Mn 3 O 4 , Fe 3 O 4 , MnAl 2 O 4 , NiAl 2 O 4 , MnFe 2 O 4 , NiFe 2 O 4 , MnNb 2 O 6 , Mn 2 Al 2 (SiO 4 ).sub. 2 and Ti 2 Nb 10 O 29 , many of which provide desirable electrical, magnetic and/or catalytic properties.
- Preferred boroaluminate glass-ceramic compositions according to the invention are those consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 20-35% Al 2 O 3 , 5-35% B 2 O 3 , and 28-60% MnO 2 , optionally including 0-15% BaO and 0-35% La 2 O 3 . These compositions provide Mn 3 O 4 and/or MnAl 2 O 4 -containing films of good quality having desirable electrical properties.
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Abstract
Suitable glass-ceramic base compositions, including some silicates, aluminosilicates, lithium aluminosilicates, and boroaluminates, are modified by the addition of suitable quantities of transition metal oxides prior to melting and forming into thermally-crystallizable glass articles. Appropriate crystallization and post-crystallization heat treatments are thereafter employed to cause crystallization of the articles and the formation and growth of films thereon, which films are characterized by the presence of transition metal compounds, typically of spinel structure, therein. Such films demonstrate useful electrical, magnetic, catalytic and/or light-absorptive properties.
Description
This application is a continuation-in-part of my copending application, Ser. No. 431,148, filed Jan. 1, 1974, and commonly assigned herewith, now U.S. Pat. No. 3,962,514.
Transition-metal-containing crystalline compounds of spinel structure are important constituents of inorganic coatings employed for an extremely wide variety of applications. For example, iron-containing spinels such as magnetite (Fe3 04), and also other ferrites such as manganese, cobalt and nickel ferrites, have been applied to a variety of organic and inorganic substrates in order to impart desirable electromagnetic properties thereto. Processes for applying such coatings and controlling the properties thereof in the course of deposition comprise a large body of technology and include vapor deposition, precipitation, evaporation and thermal decomposition techniques.
Similarly, a large number of transition metal oxides of spinel or ilmenite structure are included within the classes of catalytically-active compounds, and have been applied in the form of coatings to a variety of metal, glass and ceramic supports for use in catalytic processes. Among the transition metal oxides useful in catalysis are Mn3 O4, MnAl2 O4, MnCr2 O4, FeAl2 O4, CoAl2 O4, NiAl2 O4, CoTiO3, MnTiO3, FeTiO3, CeTiO4, CuAl2 O4 and CuCr2 O4.
In virtually all applications wherein transition metal oxide coatings are employed in combination with inorganic substrates, coating adherence and durability are extremely important properties. In many applications, binders are required to enable these coatings to demonstrate the toughness needed to withstand the shocks and abrasion of use. In the case of inorganic substrates exhibiting low surface porosity, bonding agents or high sintering temperatures are required to obtain coatings demonstrating a useful degree of adherence to the support. In the case of magnetic recording media such as magnetic memory discs, extreme surface flatness is required, compounding the difficulty of providing a durable, adherent coating.
In catalytic applications, particularly where high temperatures are involved, interactions between active oxide coatings and incompatible binders and/or supporting materials can cause reductions in activity due to the growth of inactive reaction phases or sintering. Yet the attainment of good adherence to commercial supports often requires the use of binders and/or high-temperature sintering treatments.
What is therefore desired is a means for providing transition-metal-containing oxide surface layers on compatible inorganic supports wherein bonding agents, binders, and high sintering temperatures are not required to obtain adherence, toughness and stability in the active film.
I have now devised a means of providing transition metal oxide surface films on glass-ceramic articles which overcomes the various problems of adherence, flatness, durability and thermal stability encountered in the prior art. Glass-ceramic articles are a relatively recent development in ceramic technology, the first commercially practicable articles being described by Stookey in U.S. Pat. No. 2,920,971. Briefly, the manufacture of glass-ceramics conventionally involves first compounding and melting a batch for a glass to which an amount of a crystallization-promoting or nucleating agent has been added, thereafter forming a glass article from the melt and cooling the article at least below the transformation range of the glass, and finally reheating the glass article according to a defined time-temperature schedule to produce internal nucleation and crystallization in situ thereof. The resulting article is uniformly crystallized, non-porous, free of voids, and retains the shape of the parent glass article. For a more complete description of glass-ceramic manufacturing theory and practice, reference may be made to the aforementioned Stookey patent and numerous subsequently published patents, articles and texts.
The present invention is based on the discovery that certain base glass-ceramic compositions, when modified by the addition of specified quantities of transition metal oxide modifiers, can be crystallized and thereafter heat-treated in a manner which will promote the formation and growth of transition metal oxide surface films thereon. In this way, glass-ceramic articles having integral surface films demonstrating desirable electrical, magnetic, light-absorptive and/or catalytic properties may be produced. The integral nature of these so-called exuded transition metal oxide films inherently provides the desired properties of adherence, durability and substrate compatibility.
Transition metals suitable for inclusion in glass-ceramic base compositions according to the invention include manganese, iron, cobalt, copper, chromium, nickel and vanadium. Among the useful crystalline phases which may be present in exuded transition metal oxide films produced according to the invention are Mn3 O4, Co3 O4, NiFe2 O4, MnFe2 04, CoFe2 O4, CuCr2 O4, FeCr2 O4, MnCr2 04, CoMn2 04, CoTiO3, Co2 TiO4, MnTiO3, FeTiO3, VAlO4, CuAl2 O4, CrAl2 04, NiAl2 04, FeAl2 04, CoAl2 04, MnAl2 O4, Mn2 Al2 (SiO4)2, MnNb2 06, NiNb2 06 and Ti2 Nb10 029.
In many cases, exuded transition-metal-containing films produced according to the invention also demonstrate useful light reflecting and transmitting properties. Decorative films over a wide range of colors may be produced, or transparent or translucent bodies exhibiting sharp electromagnetic cutoff values may result.
The end properties of the particular film produced depends on the composition of the base glass-ceramic composition selected as a support and upon the transition metal oxide additives selected for incorporation into the base composition.
Whereas certain of the base glass-ceramic compositions amenable to treatment according to the present invention are generally known, the capability of producing useful exuded transition-metal-containing films on glass-ceramics had been found to depend not only upon the composition of the glass-ceramic material selected as a base but also upon the nature of the subsequent treatment of the material to cause the formation and growth of useful exuded oxide films thereon. In general, the formation and growth of transition-metal-containing oxide films is promoted by heat-treating transition metal-doped glass-ceramic articles under reducing conditions at elevated temperatures for a period of time sufficient to attain the desired degree of film growth.
There is some evidence that the initiation of film formation occurs in some systems in the course of crystallization in situ of the glass precursor body. While such films are not typically sufficiently developed to be useful, the existence of the phenomenon indicates that crystallization need not be entirely complete prior to the commencement of the reduction heat treatment which is employed to achieve the growth of the exuded film. However, completion of the bulk crystallization process prior to or at least concurrently with the formation of the exuded transition-metal-containing film is normally required.
For the purposes of the present description, exuded transition-metal-containing films include not only films composed essentially entirely of transition metal oxide compounds such as MnAl2 O4, Fe3 O4, and the like, but also films wherein such compounds are in solid solution or combination with other crystalline species such as transition-metal-free aluminates, silicates, titanates, or similar compounds. Glassy matrix phases commonly found in semi-crystalline glass-ceramic materials produced from the crystallization in situ of glasses may also be present in these exuded films. In the preferred embodiments, however, crystalline transition metal oxide compounds normally comprise a predominate proportion (at least about 50% by volume) of the exuded film.
A particularly useful class of base glass-ceramic compositions suitable for treatment according to the invention are the aluminosilicate and lithium aluminosilicate compositions characterized by the presence of beta-spodumene and/or beta quartz solid solutions as principal crystal phases. This base glass composition area includes compositions consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 55-80% SiO2, 14-35% Al2 O3, 0-5% Li2 O, 0-7% TiO2, 0-10% ZrO2, 3-13% total of TiO2 + ZrO2, and 0-3% F, to which may be added a total of 0.1-10% of transition metal oxide additives. Suitable transition metal oxide additives include one or more oxides selected in the indicated proportions from the group consisting of 0-5% MnO2, 0-5% Fe2 O3, 0-3% CoO, 0-2% CuO, 0-2% Cr2 O3, 0-3% V2 O5, and 0-10% NiO. Minor amounts of other compounds may, of course, be included within these compositions as aids in melting, to modify properties, or for other known purposes. Examples of additives which have been employed are La2 O3, Nb2 O5, BaO, B2 O3, P2 O5, MgO, CaO, ZnO, Na2 O, K2 O, Ta2 O5, Cl, Br, As2 O3, and Sb2 O3. The total amount of these additives, however, is generally held to not more than about 10% by weight, so that the basic constituents SiO2, Al2 O3, Li2 O, TiO2, ZrO2, F, and transition metal oxides will comprise at least about 90% by weight of the glass-ceramic composition.
Glass-ceramic compositions within the above described composition range may be compounded and melted in accordance with conventional glass-making practice, and thereafter formed into glass articles by conventional means such as pressing, rolling, casting, spinning or the like. The batch materials may consist of oxides or may comprise any other compounds which will decompose at melting temperatures to yield molten batches having calculated oxide compositions within the aforementioned range. For these compositions, melting typically requires temperatures in the range of about 1600°-1650° C. for times in the range of about 6-16 hours.
Glass articles formed from the above compositions may be converted by crystallization in situ into semi-crystalline glass-ceramic articles according to processes conventional for beta-spodumene and beta-quartz-containing glass-ceramics. Such processes comprise exposure of the articles to temperatures in the range of about 700°-800° C. for times in the range of about 1-4hours to obtain nucleation of the glass, followed by exposure to temperatures in the range of about 800°-1200° C. for times in the range of about 1-8 hours to obtain crystallization of the glass.
Following crystallization, the semicrystalline glass-ceramic articles are subjected to further heat treatment under reducing conditions to promote the development of an exuded surface phase comprising active transition metal oxide compounds thereon. Exuded films formed in the described composition system include one or more crystalline compounds selected from the group consisting of Co3 O4,Mn3 O4, Fe3 O4, NiAl2 O4, CoAl2 O4, MnAl2 O4, FeAl2 O4, VAl2 O4 , CuCr2 O4, NiFe2 O4, CoFe2 O4, MnFe2 O4, CoTiO3, MnTiO3, FeTiO3, Co2 TiO4 and CoMn2 O4. These may be found alone, in combination with each other, or in solid solution or combination with MgAl2 O4, VAlO4, CuAl2 O4,CrAl2 O4, MnCr2 O4 and FeCr2 O4.
The film-producing heat treatments suitably comprise heating at temperatures in the range of about 500°-1000° C. in a reducing atmosphere. Preferred atmospheres include hydrogen and hydrogen-containing atmospheres such as forming gas (H2, N2). These atmospheres may contain additional constituents such as water vapor, CO, CO2, Cl2 or sulfur. Of course, other conventional reducing atmospheres such as hexane, methane, ammonia or the like may also be employed if desired. Typical treatment times range from at least about 1/2 hour up to about 10 hours or more. Longer treatment times may be employed, if desired, but long treatments are of no practical benefit and are commercially undesirable.
After sufficient growth of the transition metal oxide film has been attained in accordance with the above-described treatment, it may be desirable to further treat the article to modify the properties of the surface film for certain applications. Leaching is sometimes useful to remove residual glassy phases and/or to modify the porosity of the film. Supplemental oxidizing and/or reducing treatments may also be employed to modify the oxidation states of certain of the film constituents. The precise nature of the supplemental treatment employed, if any, will depend on the properties desired in the film and the nature of the use for which the article is intended.
Examples of thermally-crystallizable glass compositions suitable for forming beta-spodumene and beta-quartz glass-ceramics having exuded surface films containing transition metal oxide compounds according to the invention are set forth in Table I below. Compositions are given in parts by weight on the oxide basis as calculated from the batch. These compositions were batch melted in platinum crucibles at 1625° C. for 16 hours, and then poured into steel molds to form 4 inches × 4 inches × 1/2inches slabs and annealed at 650° C. Most of the compositions shown also include minor amounts of As2 O5 as a fining agent; however, the amount remaining in the glass after melting is negligible and is therefore not reported.
TABLE I __________________________________________________________________________ Composition 1 2 3 4 5 6 7 8 __________________________________________________________________________ SiO.sub.2 63.2% 60.9% 58.7% 61.2% 59.3% 71.7% 71.7% 71.7% Al.sub.2 O.sub.3 20.5 20.9 19.5 20.5 20.5 15.0 15.0 15.0 Li.sub.2 O 3.5 3.5 3.8 3.5 3.5 4.5 4.5 4.5 TiO.sub.2 4.8 4.8 4.9 4.8 4.8 5.5 5.5 5.5 ZrO.sub.2 -- -- -- 0.1 0.1 -- -- -- MgO 1.7 1.7 -- 1.7 1.7 -- -- -- ZnO 1.2 1.2 2.8 1.2 1.2 -- -- -- Na.sub.2 O 0.6 0.6 0.6 0.6 0.6 -- -- -- K.sub.2 O 0.3 0.3 0.3 0.2 0.2 -- -- -- P.sub.2 O.sub.5 1.2 1.2 2.6 1.2 1.2 -- -- -- B.sub.2 O.sub.3 0.4 0.4 -- -- -- -- -- 5.0 F 0.1 0.1 0.1 -- -- -- -- -- Br -- -- 0.4 -- -- -- -- -- MnO.sub.2 -- -- 0.4 -- -- -- -- 0.6 Fe.sub.2 O.sub.3 1.6 3.0 4.0 3.0 3.0 -- 1.3 -- CoO -- -- 0.9 0.6 2.4 2.6 -- 2.7 Nb.sub.2 O.sub.5 -- -- -- -- -- 3.5 -- -- __________________________________________________________________________
The thermally-crystallizable glass articles in Table I, produced as above described, are thereafter treated as set forth below in Table II in order to produce glass-ceramic articles having beta-spodumene and/or beta-quartz solid solutions as principal crystalline phases and exuded surface films containing transition metal oxide compounds. Table II reports the crystallizing heat treatments employed to convert each thermally-crystallizable glass article to the semi-crystalline state, the principal crystal phase present in the articles after ceramming, the reducing heat treatments employed to promote the growth of transition metal oxide compounds present in the exuded surface films, the appearance of the articles after the growth treatments, and the dominant properties of the exuded films. The principal crystalline phases listed are generally solid solutions rather than specific compounds. In instances where forming gas is used as the reducing atmosphere, a gas consisting of 8% H2 and 92% N2 by volume was employed. Typical film thicknesses over the range of growth treatments employed range about 0.1-2 microns.
TABLE II __________________________________________________________________________ 1 2 3 4 __________________________________________________________________________ Nucleation Treatment 2 hours - 780° C. 2 hours - 780° C. 2 hours - 780° C. 2 hours - 780° C. Crystallizaton 6 hours - 1080° C. 2 hours - 1100° C. 2 hours - 1100° C. 2 hours - 1100° C. Treatment Principal Crystal β-spodumene, ana- β-spodumene, ana- β-spodumene, ana- β-spodumene, Phases tase, MgAl.sub.2 O.sub.4 tase, MgAl.sub.2 O.sub.5 tase, ZrAl.sub.2 O.sub.4 anatase Film Growth Treatment 2 hours - 500° C. 2 hours - 500° C. 2 hours - 500° C. 2 hours - 500° C. H.sub.2 H.sub.2 H.sub.2 forming gas Surface Appearance purple metallic black black metallic grey black Exuded Crystal Phases FeAl.sub.2 O.sub.4 Fe.sub.3 O.sub.4, FeAl.sub.2 O.sub.4, Fe.sub.3 O.sub.4, CoAl.sub.2 O.sub.4, CoAl.sub.2 O.sub.4, Fe.sub.3 O.sub.4 Mn.sub.3 O.sub.4, MnFe.sub.2 O.sub.4 Surface Properties magnetic - good magnetic - good magnetic - good magnetic - good hysteresis loop hysteresis loop hysteresis loop hysteresis loop 5 6 7 8 __________________________________________________________________________ Nucleation Treatment 2 hours - 780° C. 2 hours - 780° C. 2 hours - 780° C. 2 hours - 780° C. Crystallizaton 2 hours - 1080° C. 2 hours - 1100° C. 2 hours - 1100° C. 2 hours - 1100° C. Principal Crystal β-spondumene, β-spodumene, β-spodumene, β-spodumene, CoTiO.sub.3, Phases anatase CoTiO.sub.3, Co.sub.2 TiO.sub.4 CoTiO.sub.3 Co.sub.2 TiO.sub.4 Film Growth Treatment 2 hours - 500° C. 2 hours - 500° C. 2 hours - 500° C. 2 hours - 500° C. forming gas forming gas forming gas forming gas Surface Appearance grey black black black black Exuded Crystal Phases CoAl.sub.2 O.sub.4, Co.sub.3 O.sub.4, Co.sub.3 O.sub.4, Co.sub.2 TiO.sub.4, Fe.sub.3 O.sub.4, TiFe.sub. Co.sub.3 O.sub.4, Mn.sub.3 O.sub.4, CoMn.sub.2 O.sub.4, Fe.sub.3 O.sub.4, CoFe.sub.2 O.sub.4 CoTiO.sub.3 CoTiO.sub.3 Surface Properties magnetic - good active catalyst active catalyst very active catalyst, hysteresis loop C.sub.6 H.sub.8 oxidation CO oxidation CO oxidation, C.sub.6 H.sub.8 C.sub.6 H.sub.8 oxidation oxidation __________________________________________________________________________
From the foregoing examples it is readily apparent that a broad range of aluminosilicate and lithium aluminosilicate glass-ceramic compositions containing transition metal additives may be treated according to the invention to provide exuded transition metal spinel films thereon having a variety of uses.
Compositions which are utilized for producing transition metal films having desirable magnetic and electrical properties are titania-nucleated lithium aluminosilicate compositions consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 58-64% SiO2, 19-21% Al2 O3, 2-5% Li2 O, 2-7% TiO2, 0-1% ZrO2, 3-7% total of TiO2 + ZrO2, 0-1% F, and 1-6% total of transition metal additives, essentially including iron, selected in the indicated proportion from the group consisting of 1-5% Fe2 O3, 0-5% MnO2, 0-5% CoO and 0-3% NiO. Exuded transition metal films produced from articles of these compositions typically include one or more compounds of spinel structure selected from the group consisting of Co3 O4, Fe3 O4, Mn3 O4, MnAl2 O4, FeAl2 O4, CoAl2 O4, MnFe2 O4, NiFe2 O4, and CoFe2 O4, essentially including at least one iron compound. Example I of Table I represents the presently preferred composition for producing a film having particularly desirable magnetic properties according to the invention.
Compositions which are utilized for producing glass-ceramic articles having exuded transition metal oxide films demonstrating useful catalytic activity consist essentially, in weight percent on the oxide basis as calculated from the batch of about 68-74% SiO2, 14-19% Al2 O3, 0-5% Li2 O, 0-6% TiO2, 0-3% ZrO2, 5-9% total TiO2 + ZrO2, 0-5% B2 O3, 0-3% F, and 1-10% total of transition metal additives selected in the indicated proportion from the group consisting of 0-5% Fe2 O3, 0-5% CoO, 0-5% MnO2, 0-2% CuO, 0-2% Cr2 O3, and 0-3% NiO. Exuded transition metal films produced on articles of these compositions typically contain one or more compounds selected from the group consisting of CoTiO3, Co2 TiO4 CoMn2 O4, Co3 O4, Mn3 O4, CoFe2 O4, CoAl2 O4, MnTiO3, and FeTiO3. Example 8 of Table I represents the presently preferred composition for producing a catalytically-active oxide film in this system.
Types of glass-ceramic articles other than alumino-silicate and lithium aluminosilicate beta-quartz and beta-spodumene articles are also useful in providing exuded transition-metal-containing films according to the invention. Another useful composition area is found to include somewhat diverse silicate, aluminosilicate, and boroaluminate base compositions wherein manganese is a major constituent, comprising at least about 10% by weight of the compositions. The operative composition area includes compositions consisting essentially, in weight percent on the oxide basis, as calculated from the batch, of about 10-60% MnO2, at least one oxide selected in the indicated proportion from the group consisting of 10-70% SiO2, 13-43% Al2 O3,and 0-35% B2 O3, essentially including at least about 5% B2 O3 and 20% Al2 O3 , when SiO2 is absent, not exceeding about 5% B2 O3 when Al2 O3 is absent, and not exeeding about 10% B2 O3 when both SiO2 and Al 2 O3 are present, the sum total of MnO2 + SiO2 + Al2 O3 + B2 O3 comprising at least about 60% by weight of the composition, 0-30% Nb2 O5, 0-20% TiO2, 0-5% Fe2 O3, 0-10% NiO, 0--3% Cr2 O3, 0-10% ZrO2, 0-35% La2 O3, 0-10% Ta2 O5, 0-15% BaO, 0-10% SnO2, 0-3% CoO, 0-4% ZnO and 0-10% K2 O.
MInor amounts of other compounds may, of course, be included within these compositions as aids in melting, to modify properties and so forth, including, for example, Li2 O, Na2 O, WO3, P2 O5, MgO, Cl, F, MnO3, Cu2 O, V2 O5, As2 O3, and Sb2 O3.
Glass-ceramic compositions within the aforementioned composition range may be melted according to conventional practice, typically at temperatures in the range of about 1500-1600° C. for times on the order of about 6-16 hours. The molten glasses may be formed into glass articles by conventional means such as pressing, rolling, casting, drawing or the like. Batch materials for these glasses may comprise oxides or other compounds which will decompose at melting temperatures to yield molten batches having oxide compositions within the aforementioned range.
Glass articles formed from the above compositions may be converted by crystallization in situ into glass-ceramic articles by heat treatment at temperatures in the range of about 600°-1200° C. for times in the range of about 4-24 hours. Useful crystallization treatments comprise a nucleation step wherein the article is heated at temperatures in the range of about 600°-800° C. for times on the order of 1-4 hours. Principal crystal phases in these composition systems include MnAl2 O4, Mn3 O4, Mn2 Al2 (SiO4)2 and MnSiO3 depending somewhat on the composition of the MnO2 -(B2 O3, Al2 O3, SiO2) base glass.
Following crystallization, the growth of transition-metal-containing oxide films on the surface of these glass-ceramic articles is promoted using reducion heat treatments substantially the same as those above described for beta-spodumene and beta-quartz-containing articles. Such treatments typically comprise heating to temperatures in the range of about 500°-1000° C. in a reducing atmosphere, preferably an atmosphere comprising hydrogen or nitrogen-hydrogen forming gas, for treatment times in the range from about 1/2 hour up to about 10 hours, or more. Again, longer treatments may be employed if desired, but these are not deemed of practical benefit.
Transition-metal-containing exuded films which may form in this composition system include Mn3 O4, Fe3 O4, MnAl2 O4, NiAl2 O4, NiFe2 O4, MnFe2 O4, MnCr2 O4,MnNb2 O6 NiNb2 O6, Mn2 Al2 (SiO4)2, and Ti2 Nb10 O29. The compounds in this system may be found either alone or in solid solution or combination with other crystalline species such as MnSiO3 and ZrO2. Residual glassy phases may also be present. Whereas the transition metal oxide films produced in these systems typically differ in composition from the interior of the article, it is possible that in certain cases the predominant surface compound is also one which predominates in the article as a whole. Nevertheless treatment according to the invention is effective to increase crystal formation in the surface layers of the article such that improved surface properties are obtained.
Examples of thermally-crystallizable glass compositions suitable for forming silicate, aluminosilicate, and boroaluminate glass-ceramics having exuded surface films containing transition metal oxide compounds according to the invention are set forth in Table III below. Compositions are given in parts by weight on the oxide basis as calculated from the batch. The compositions were batch melted in platinum crucibles at 1600° C. for about 6 hours, and then poured into steel molds to form 3/8 ×5 × 5 inch slabs and annealed at about 600° C. A few of the compositions additionally contained minor amounts of As2 O5 as a fining agent, but the amount remaining in the glass after melting is small and is therefore not reported.
TABLE III __________________________________________________________________________ Compositon 9 10 11 12 13 14 15 16 __________________________________________________________________________ MnO.sub.2 43.0% 31.8% 45.0% 60.0% 51.5% 21.0% 40.0% 30.0% B.sub.2 O.sub.3 -- -- 30.0 5.0 -- -- -- -- Al.sub.2 O.sub.3 20.6 15.1 25.0 20.0 13.3 43.0 25.0 20.0 SiO.sub.2 35.4 19.7 -- -- 22.2 34.0 25.0 30.0 La.sub.2 O.sub.3 -- 33.5 -- -- -- -- -- -- Nb.sub.2 O.sub.5 -- -- -- -- 13.0 -- -- -- Ta.sub.2 O.sub.5 -- -- -- -- -- 5.0 -- -- TiO.sub.2 10.0 -- -- -- -- -- -- -- SnO.sub.2 -- -- -- -- -- -- -- 10.0 K.sub.2 O -- -- -- -- -- -- -- 10.0 BaO -- -- -- 15.0 -- -- -- -- ZnO -- -- -- -- -- 2.0 -- -- Cr.sub.2 O.sub.3 -- -- -- -- -- 1.0 -- -- Fe.sub.2 O.sub.3 -- -- -- -- -- 3.0 -- -- CoO -- -- -- -- -- 1.0 -- -- NiO -- -- -- -- -- 3.0 10.0 -- __________________________________________________________________________
The thermally-crystallizable glass articles of Table III, produced as above described, are thereafter treated as set forth below in Table IV in order to produce glass-ceramic articles having exuded surface films containing transition metal oxide compounds. Table IV reports the crystallization heat treatments employed to obtain bulk crystallization in situ of the articles, the principal crystalline phases present in the articles after ceramming, the reducing heat treatments employed to promote the growth of transition metal spinel films on the articles, the transition metal spinels present in the exuded surface films, the appearance of the articles after growth treatment, and the dominant properties of the exuded films. Film dielectric constant (K') and loss tangent (tan δ) are reported where determined on individual samples. In instances where forming gas is reported as present in the reducing atmosphere, a gas consisting of 8% H2 and 92% N2 by volume was employed. Typical film thicknesses for these exuded films over the range of growth treatments employed range about 0.1-4 microns.
TABLE IV __________________________________________________________________________ 9 10 11 12 __________________________________________________________________________ Nucleation Treatment 4 hours - 650° C. 4 hours - 650° C. 4 hours - 700° C. 4 hours - 650° C. Crystallization 2 hours - 800° C. 4 hours - 800° C. 4 hours - 800° C. 2 hours - 1000° C. Treatment 4 hours - 1000° C. 4 hours - 1000° C. Principal Crystal MnSiO.sub.3, MnSiO.sub.3 Mn.sub.3 O.sub.4 Phases Mn.sub.2 Al.sub.2 (SiO.sub.4).sub.2 Film Growth 4 hours - 1000° C. 4 hours - 800° C. 2 hours - 500° C. 2 hours - 700° C. Treatment H.sub.2 forming gas forming gas forming gas Surface Appearance liver color liver color brown grey brown Exuded Crystal Phases Mn.sub.3 O.sub.4, MnAl.sub.2 O.sub.4 MnAl.sub.2 O.sub.4, Mn.sub.3 O.sub.4 Mn.sub.3 O.sub.4, MnAl.sub.2 O.sub.4 MnAl.sub.2 O.sub.4, Mn.sub.3 O.sub.4 Surface Properties ferromagnetic ferromagnetic ferromagnetic ferromagnetic K' = 15.5 K' = 14.0 K' = 8.7 K' = 14.8 tanδ = 0.042 tanδ = 0.002 tanδ = 0.06 tanδ = 0.53 13 14 15 16 __________________________________________________________________________ Nucleation Treatment 4 hours - 650° C. 4 hours - 650° C. 4 hours - 780° C. 4 hours - 650° C. Crystallization 2 hours - 1000° C 4 hours - 1000° C. 4 hours - 1000° C. 2 hours - 700° C. Treatment Principal Crystal MnSiO.sub.3 MnAl.sub.2 O.sub.4 MnSiO.sub.3 Phases Film Growth 2 hours - 700° C. 2 hours - 800° C. 2 hours - 1000° C. 2 hours - 500° C. Treatment forming gas forming gas forming gas forming gas Surface Appearance brown black black brown grey Exuded Crystal Mn.sub.2 Al.sub.2 (SiO.sub.4).sub.2, Mn.sub.3 O.sub.4, MnAl.sub.2 O.sub.4 Mn.sub.3 O.sub.4, MnAl.sub.2 O.sub.4, Mn.sub.3 O.sub.4, MnAl.sub.2 O.sub.4 Phases MnNb.sub.2 O.sub.6 NiAl.sub.2 O.sub.4 Surface Properties ferromagnetic ferromagnetic; ferromagnetic; ferromagnetic active catalyst active catalyst (CO, C.sub.6 H.sub.8 oxida- (CO, C.sub.6 H.sub.8 oxida- tion) tion) K' = 14.8 K' = 12.4 K' = 12.0 tanδ = 0.038 tanδ = 0.016 tanδ = 0.01 __________________________________________________________________________
While the foregoing examples indicate that a broad range of manganese-containing compositions may be treated according to the invention to provide exuded crystalline films thereon, the best film properties are produced over a somewhat narrower range of composition. Among the aluminosilicate glass-ceramic compositions amenable to treatment according to the invention, those consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 19-40% SiO2, 13-43% Al2 O3, and 15-50% MnO2, optionally including 0-4% ZnO, 0-10% TiO2, 0-10% ZrO2, 0-10% SnO2, 0-10% NiO, 0-5% Fe2 O3, and 0-30% Nb2 O5, are preferred. These compositions may provide exuded films containing at least one of Mn3 O4, Fe3 O4, MnAl2 O4, NiAl2 O4, MnFe2 O4, NiFe2 O4, MnNb2 O6, Mn2 Al2 (SiO4).sub. 2 and Ti2 Nb10 O29, many of which provide desirable electrical, magnetic and/or catalytic properties.
Preferred boroaluminate glass-ceramic compositions according to the invention are those consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 20-35% Al2 O3, 5-35% B2 O3, and 28-60% MnO2, optionally including 0-15% BaO and 0-35% La2 O3.These compositions provide Mn3 O4 and/or MnAl2 O4 -containing films of good quality having desirable electrical properties.
From the foregoing description it is apparent that a large number of exuded transition metal oxide films may be provided on glass-ceramic base articles according to the invention to impart a variety of useful properties thereto. Thus articles having configurations suitable for use as magnetic memories, such as discs, may be conventionally formed, crystallized and provided with flat surfaces, and thereafter heat treated to exude magnetic transition metal oxide films thereon. Similarly glass-ceramic tubes, honeycombs, or the like may be formed, heat treated to exude catalytically-active films thereon, and incorporated into catalytic reactors to provide stable, durable active elements. Of course, these examples are merely illustrative of the numerous applications for glass-ceramic articles having integral exuded films which may be practiced within the scope of the present invention as defined by the appended claims.
Claims (8)
1. A method of providing a glass-ceramic article having an exuded surface film comprising at least one transition metal compound selected from the group consisting of Mn3 O4, Fe3 O4, Co3 O4, NiAl2 O4, CoAl2 O4, MnAl2 D4, 2O4, ValO4, NiFe2 O4, CoFe2 O4, MnFe2 O4, MnTiO3, CoTiO3, FeTiO3, Co2 TiO4 and CoMn2 O4 on at least a portion of the surface thereof which comprises the steps of:
a. compounding a batch for a glass composition consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 55-80% SiO2, 14-35% Al2 O3, 0-5% Li2 O, 0-7% TiO2, 0-10% ZrO2, 3-13% total of said TiO2 + ZrO2, 0-3% F, and 0.1-10% total of transition metal oxide additives containing one or more of the transition metals manganese, iron, cobalt, chromium, nickel and vanadium in a combination which will provide one or more of said Mn3 O4, Fe3 O4, Co3 O4, NiAl2 O4, CoAl2 O4, MnAl2 O4, FeAl2 O4, VAlO4, NiFe2 O4, CoFe2 O4, MnFe2 O4, MnTiO3, CoTiO3, FeTiO3, Co2 TiO4 and CoMn2 O4 transition metal compounds on the surface of said article, said additives being selected in the indicated proportions from the group consisting of 0-5% MnO2, 0-5% Fe2 O3, 0-3% CoO, 0-2% Cr2 O3, 0-3% V2 O5 and 0-10% NiO, the foregoing constituents comprising at least about 90% by weight of said composition and said composition being capable of forming a principle crystal phase selected from the group consisting of beta-spodumene and beta-quartz solid solutions upon thermal crystallization thereof;
b. melting said batch at a temperature in the range of about 1600°-1650° C. for a time in the range of about 6-16 hours to provide a molten glass;
c. forming the molten glass into a glass article;
d. exposing the glass article to a temperature in the range of about 700°-800° C. for a time in the range of about 1-4 hours to obtain nucleation of the glass;
e. thereafter exposing the article to a temperature in the range of about 800°-1200° C. for a time in the range of about 1-8 hours to obtain crystallization of the glass by the formation of a principal crystal phase selected from the group consisting of beta-quartz and beta-spodumene solid solution therein; and
f. exposing the article to a temperature in the range of about 500°-1000° C. in a reducing atmosphere for a time in the range of about 1/2-10 hours to develop said exuded surface film comprising said transition metal compounds thereon.
2. A method in accordance with claim 1 wherein the reducing atmosphere is selected from the group consisting of hydrogen and forming gas.
3. A method in accordance with claim 1 wherein:
a. the batch is compounded to provide a glass composition consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 58-64% SiO2, 19-21% Al2 O3, 2-5% Li2 O, 2-7% TiO2, 0-1% ZrO2, 3-7% total of TiO2 + ZrO2, 0-1% F, and 1-6% total of transition metal oxide additives, essentially including iron, selected in the indicated proportions from the group consisting of 1-5% Fe2 O3, 0-5% MnO2, 0-5% CoO and 0-3% NiO, and
b. the exuded surface film comprises at least one transition metal compound, essentially including at least one compound of iron, selected from the group consisting of Co3 O4, Fe3 O4, Mn3 O4, MnAl2 O4, FeAl2 O4, CoAl2 O4, NiAl2 O4, MnFe2 O4, NiFe2 O4 and CoFe2 O4 and exhibits magnetic hysteresis.
4. A method in accordance with claim 1 wherein:
a. the batch is compounded to provide a glass composition consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 68-74% SiO2, 14-19% Al2 O3, 0-5% Li2 O, 0-6% TiO2, 0-3% ZrO2, 5-9% total of TiO2 + ZrO2, 0-5% B2 O3, 0-3% F, and 1-10% total of transition metal additives selected in the indicated proportion from the group consisting of 0-5% Fe2 O3, 0-5% CoO, 0-5% MnO, 0-2% Cr2 O3, and 0-3% NiO, and
b. the exuded surface film comprises at least one transition metal compound selected from the group consisting of CoTiO3, Co2 TiO4, CoMn2 O4, Co3 O4, Mn3 O4, Fe3 O4, CoFe2 O4, CoAl2 O4, MnTiO3, and FeTiO3 and exhibits catalytic activity for oxidation.
5. A method of providing a glass-ceramic article having an exuded ferromagnetic surface film comprising at least one transition metal compound selected from the group consisting of Mn3 O4, Fe3 O4, MnAl2 O4, NiAl2 O4, NiFe2 O4, MnFe2 O4, MnCr2 O4, MnNb2 O6, NiNb2 O6, Ti2 Nb10 O29, and Mn2 Al2 (SiO4)2 on at least a portion of the surface thereof which comprises the steps of:
a. compounding a batch for a glass composition consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 10-60% MnO2, at least one oxide selected in the indicated proportion from the group consisting of 10-70% SiO2, 13-43% Al2 O3, and 0-35% B2 O3, essentially including at least about 5% B2 O3 and 20% Al2 O3 when SiO2 is absent, not exceeding about 5% B2 O3 when Al2 O3 is absent, and not exceeding about 10% B2 O3 when both SiO2 and Al2 O3 are present, at least about 60% total of MnO2 + SiO2 + Al2 O3 + B2 O3, 0-30% Nb2 O5, 0-35% La2 O3, 0-10% Ta2 O5 , 0-15% BaO, 0-10% SnO2, 0-4% ZnO, 0-10% ZrO2, 0-20% TiO2, 0-5% Fe2 O3, 0-10% NiO, 0-3% Cr2 O3, 0-3% CoO and 0-10% K2 O;
b. melting the batch at a temperature in the range of about 1500°-1600° C. for a time in the range of about 6-16 hours;
c. forming the molten glass into a glass article;
d. exposing the glass to a temperature in the range of about 600°-1200° C. for a time in the range of about 4-24 hours to obtain crystallization of the glass; and
e. exposing the crystallized glass to a temperature in the range of about 500°-1000° C. in a reducing atmosphere for a time in the range of about 1/2-10 hours to develop said exuded surface film comprising said transition metal compounds therein.
6. A method in accordance with claim 5 wherein the reducing atmosphere is selected from the group consisting of hydrogen and forming gas.
7. A method in accordance with claim 5 wherein:
a. the batch is compounded to provide a glass consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 19-40% SiO2, 13-43% Al2 O3, 15-50% MnO2, 0-4% ZnO, 0-10% TiO2, 0-10% ZrO2, 0-10% SnO2, 0-10% NiO, 0-5% Fe2 O3, and 0-3% Nb2 O5, and
b. the exuded surface film comprises at least one transition metal compound selected from the group consisting of Mn3 O4, Fe3 O4, MnAl2 O4, NiAl2 O4, MnFe2 O4, NiFe2 O4, MnNb2 O6, NiNb2 O6, Ti2 Nb10 O29 and Mn2 Al2 (SiO4)2.
8. A method in accordance with claim 5 wherein:
a. the batch is compounded to provide a glass consisting essentially, in weight percent on the oxide basis as calculated from the batch, of about 20-35% Al2 O3, 5-35% B2 O3, 28-60% MnO2, 0-15% BaO and 0-35% La2 O3 ; and
b. the exuded surface film comprises at least one transition metal compound selected from the group consisting of Mn3 O4, and MnAl2 O4.
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